As long as everything is gemmed / reforged to favor mastery it doesn't matter after that.
Breakpoints are completely irrelevant in this scenario. They absolutely don't HAVE to pick one, there's literally no difference between balancing haste and crit vs stacking haste vs stacking crit or anything in-between. You'll see the same end results no matter what and the rest comes down to personal play.
If you think it makes a tangible difference doing X or Y in the haste vs crit dept. you need to do a bit more homework on it. It's not a matter of opinion at this point in the xpac.